Darren McFadden is probably going to miss the Broncos game and maybe more. The Raiders haven't said anything of the sort, but—as Steve Corkran tells us—the Raiders worked out two running backs on Wednesday. They would not do this unless they were worried about Darren McFadden's chances of playing in their next game.
Of course, the Raiders could be doing this just as a precaution, but Hue Jackson hasn't been rushing players back from injury, which leads me to the conclusion that McFadden will be able to play at least the next game.
As awesome as McFadden is, this injury is one the Raiders can survive. Michael Bush is a very capable backup, and Taiwan Jones is an amazing third string option.
The Raiders will still have their bash and slash mix. It will now just be with the Bash being in the primary role. As long as the Raiders can get anything going in the pass game and keep defenses honest, they will still be able to run the ball.